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What Causes Chronic Hyperventilation & What You Can Do About It

PART 3: What Causes Low CO2?

This article is the third of a series exploring the questions of what might be causing chronic and resistant over-breathing or hyperventilation, and secondly what we might do to address this situation. Chronic over-breathing shows up as stubbornly low carbon dioxide readings from a capnometer, which is the biofeedback device I use for breathing training in the Stress Resilient Mind programme. The articles are aimed primarily at people experiencing such issues, but I hope they'll be relevant to health practitioners too.

So far in the series:

In this article we'll use our understanding of this underlying physiology to fill out our two causal accounts in greater depth.

Brief Summary of Acid-Base Physiology

In the last article we started to look at acid-alkali balance in the body, and saw that:

  • The body needs to regulate pH or acidity level, especially that of the blood. That is, pH must be kept within tight bounds, otherwise various physiological processes don't work properly.
  • The process of energy production within cells creates acids as a bi-product, and to maintain its balance the body needs to get rid of excess acid.
  • Carbon dioxide is the main acid produced by cells, and it is the main determinant of blood acidity.
  • The body has two systems for regulating pH, in effect by excreting acid from the body.
  • The lungs excrete carbon dioxide by breathing it out. This is the primary system, and the faster.
  • The secondary system is the bicarbonate buffer system, operating in the kidneys, which can excrete both hydrogen ions and bicarbonate ions and adjust the relative levels of each. The kidney system is slower acting.

Now we're in a position to go into the two alternative accounts of over-breathing in more depth.

Chronic Stress Account

Once again, the first account is that the root cause of the problem is stress-related over-breathing. In the short term, over-breathing pulls the blood out of it's healthy pH range, by blowing off too much carbon dioxide. The blood is now too alkaline, a state called alkalosis. The consequence is that brain cells in particular get a reduced oxygen supply, because (i) blood vessels in the brain constrict and (ii) oxygen is bound too tightly too the blood (haemoglobin).

If this state of affairs (i.e. over-breathing) carries on for long enough – and that means really just a few hours – then the secondary regulation system kicks in to correct the blood pH.

The kidneys act to compensate for the over-breathing by changing the excretion or retention of bicarbonate and hydrogen ions – in this case by excreting relatively more of bicarbonate into the urine. In this case the urine becomes relatively more alkaline.

So now the alkalosis has been corrected, at least to a degree, and you don't feel as bad. But this state of affairs is still far from optimal.

You're going to be somewhat deficient in bicarbonate, and that means your system has lost some of it's ability to buffer, or to smooth out natural variations (in blood pH). In practical terms, it means that if some more stress comes along, either physical or emotional, you're going to be more easily tipped out pH balance and into alkalosis again. This is something I've seen with clients: it's easy for them to lower end-tidal carbon dioxide as measured by the capnometer (which is known to correlate to blood carbon dioxide concentration). That means they're going to be less resilient to stress.

Another consequence seems to be that you're going to be more prone to fatigue.

Energy Metabolism Account

The second causal account is that the root of the apparent breathing dysregulation is not over-breathing at all but is to do with cellular energy production. The over-breathing is an adaptive, or helpful, compensation for this underlying problem.

To understand this, we need to say more about cellular energy production.

Cellular Energy Production

To recap, cellular energy production is a biochemical process whereby fuel derived from foods is burned to liberate energy. It's comparable to a car engine where petrol is burned in a controlled way, and the liberated energy is used to drive the vehicle forward.

In human cells, and in fact all animal cells, the liberated energy is captured by a molecule called ATP, adenosine triphosphate.

Cellular energy production happens mainly within cell structures called mitochondria, which you may have heard of. That is to say, most ATP is produced within mitochondria.

An ATP molecule is like a miniature rechargeable battery – once it's captured some energy it moves out of the mitochondria and around in the cell to where the energy is needed for the normal functioning of the cell, e.g. building new protein molecules.

Once it has discharged its energy, the molecule of ATP has now become ADP, adenosine diphosphate, and it needs to be recycled back into the energy production process, back into the mitochondria, so it can be recharged.

Burning Fuel For Energy

In broad terms, there are two main ways of creating energy. These are called aerobic respiration and anaerobic respiration. Don't let the word respiration confuse you, this is nothing to do with mechanical breathing.

Aerobic energy production means the burning of fuel in the presence of oxygen. Anaerobic means no oxygen is involved. It may surprise you to learn that we don't need oxygen to produce energy, but we can – well partially anyway. In fact anaerobic energy production is much less efficient than aerobic, producing only a fraction of the energy, and alone it wouldn't be enough to sustain us – as you know, we die without oxygen.

We normally only use anaerobic energy production in exceptional circumstances, typically when we need short, intense bursts of energy, for example when sprinting. Over the short term anaerobic energy production can boost our energy output, but after that we're spent and we need to stop and recover.

There are two main fuel sources. These are fat and sugar (the latter mainly in the form of glucose, and derived from carbohydrates in the diet). So:

glucose + O2 → CO2 + H2O + energy

and similarly:

fat + O2 → CO2 + H2O + energy

(Actually fat burning is more efficient in the sense that it produces less in the way of "exhaust fumes" known as free radicals.)

So carbon dioxide is the bi-product of aerobic energy production (either fat or carbs). However in anaerobic energy production, no carbon dioxide is produced, but instead the bi-product is lactic acid. This is the second of the metabolic acids that I mentioned in part 2 of the series.

Lactic Acid

Lactic acid is rather unpleasant stuff. It's what makes your muscles hurt when you exercise vigorously. It also correlates with anxiety – there's even some evidence that injecting lactic acid triggers panic attacks.

It's easy to get rid of carbon dioxide – we just breathe it out, and the body is well adapted for this. Not so for lactic acid. It's hard to shift, and it tends to hang around particularly in muscles where it is most commonly created – that's partly why muscles can feel sore for days after intensive exercise.

So besides being much less efficient, anaerobic respiration has this further drawback that it creates acid which tends to hang around. Of course, the body needs to keep pH (acidity) balanced, particularly in the blood as we've seen. But if you've got a lot of extra acidity in the form of lactic acid, you can still return your pH to balance by getting rid of the other acid – carbon dioxide. How do you do this? – by breathing more.

Now you can start to see how over-breathing can be an adaptive compensation for an underlying problem, which is excessive lactic acid production.

Mytochondrial Dysfunction

Healthy people should only need to use anaerobic energy production occasionally in times of high demand for energy, e.g. sprinting. After such a short period of high demand, you recover, and eventually get rid of the lactic acid, and all is well.

But if you're not healthy, and particularly if you have mitochondrial dysfunction, then it may be that your cells rely on some anaerobic energy production much more frequently, for only mild exertion – or even all the time in serious cases. Then lactic acid can build up in the body – this is known as lactic acidosis.

Mitochondrial dysfunction is a process that underlies pretty much all chronic illnesses. The predominant symptom is fatigue.

This is the part of my account which is more speculative, less established science.

Many people including a lot of health practitioners think that mitochondrial dysfunction is only happening to a significant extent in extreme cases of fatigue and poor health. But it may be that it's far more common than that.

Dr Frank Shallenberger MD is an energy and anti-aging specialist who focuses assessing mitochondrial function in his patients. For that end he developed  a sophisticated system which he calls bio-energy testing (and which he describes in his book "Bursting With Energy"). Dr Shallenberger believes that mitochondrial dysregulation and decay is the fundamental pathway behind all chronic disease, and furthermore, he thinks mitochrondrial dysregulation begins well before any symptoms appear. According to Dr Shallenberger one of the first consequences is increased reliance on anaerobic respiration.

You can learn more about Dr Shallenberger's thinking via a four-part video series he's published on YouTube. I've linked to part one below.

I should add there are other potential causes for the build-up of excess lactic acid, e.g. hypoperfusion (inadequate blood supply to the affected tissue) or gut flora imbalances.

Breathing Dysregulation Again

Suppose you do have a significant level of lactic acid production, e.g. due to mitochondrial dysfunction. As I said, your body needs to compensate for the excess acid production, and it does this by breathing more and getting rid of more carbon dioxide, which is the main metabolic acid and easy to get rid of.

This would show up as a chronically low carbon dioxide level as measured by the capnometer. Not only would CO2 be low, it would be very hard to fully correct, just by working to change your breathing pattern. In effect, the body has no choice but to over-breathe.

What about the bicarbonate buffering system? Well, chances are that it's acting to support the breathing regulation system to get rid of the extra acid in the system. The kidneys will get rid of more hydrogen ions and less bicarbonate, compared to the (stress-related) genuine over-breathing scenario.

As far as I know Dr Schallenberger's assessment system doesn't make use of capnometry, but if he's right, then a relatively early sign of mitochondrial dysfunction could be a fall in end-tidal carbon dioxide as measured by a capnometer. To repeat a point I made in an earlier article, it's certainly my experience that clients who are generally unwell (e.g. have something like chronic fatigue syndrome) tend to have lower (and stubbornly low) baseline carbon dioxide readings.


We've covered in more depth the two main causal accounts of persistently low carbon dioxide levels measured in the breath.

  • The first is truly a breathing dysregulation: over-breathing, probably related to stress, has become a persistent pattern and the bicarbonate buffering system has been forced to compensate in order to bring the blood pH back to balance. Breathing regulation and bicarbonate buffering aren't working together, but in a sense against each other. The result is a non-optimal state of functioning.
  • The second possible causal account is that the regulatory systems are working to counter an underlying problem of a different nature. Problems with cellular energy production have lead to excessive lactic acid, and over-breathing is an adaptive response to this.

So if you have persistently low CO2 levels what you need to do is find out which of these two situations is in play for you, and then respond appropriately, addressing the underlying causes.

That's what we'll turn to in the next article in the sequence (part 4).

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